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Q.We’re installing a fiberglass tub unit over a truss-framed floor. A small plan change moved the tub so that the overflow pipe lines up with a floor truss below. There’s just enough room to run the drain above the truss, but is it okay to run the drain horizontally for a foot or so beyond where the overflow standpipe connects before putting in the trap? The code we use says there can be no more than 24 inches between the drain and the trap weir, and to place the trap “as close as possible” to the drain, but what does this mean in terms of horizontal distance?

A.Mike Casey, a licensed plumber in Connecticut and California and coauthor of Code Check Plumbing, responds: Most code inspectors will allow 24 inches of horizontal distance before the trap where necessary, but be sure to check with your local official. There also are offset tub drain-overflow assemblies with side or rear outlets that may help overcome framing obstacles.

Tub Drain Distances